The present invention relates to a method for producing an aluminum support which is used as a support for lithographic printing plates.
The present invention also relates to a method for producing an aluminum support, including surface roughening of an aluminum support which is used as a support for lithographic printing plates, more specifically, the present invention relates to a method suitable for the surface roughening of an aluminum plate prone to generation of rush mat-like wrinkles called streaks ascribable to the difference in the orientation of crystal grains or generation of granular treatment unevenness called plane quality unevenness, which are readily occur in conventional chemical etching treatments.
Furthermore, the present invention relates to a method for producing an aluminum support for lithographic printing plates, which can attain uniform surface roughening of an aluminum plate containing many impurities and having bad graining property.
The surface roughening of an aluminum support for lithographic printing plates is generally performed by an AC etching method where an ordinary sinusoidal AC current or a special alternating waveform current such as rectangular waveform current is used. Using a suitable electrode such as graphite as a counter electrode, the surface roughening of the aluminum plate is usually performed by a single treatment. However, the depth of pits obtained is generally shallow and the resulting aluminum support has a short press life. Therefore, various methods have been heretofore proposed so as to obtain an aluminum plate having a grained surface suitable for printing plates, where pits having a depth larger than the diameter thereof are uniformly and densely present. Known examples of these methods include a surface roughening method using a special electrolytic power source waveform (see, JP-A-53-67507 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d)), a ratio between the quantity of electricity at an anode time and the quantity of electricity at a cathode time in an electrolytic surface roughening using AC (see, JP-A-54-65607), a power source waveform (see, JP-A-56-25381), a combination with the quantity of current passed per the unit area (see, JP-A-56-29699).
On the other hand, with respect to the method for producing an aluminum support, an aluminum support prepared as follows has been used as a support for lithographic printing plates. An aluminum ingot melted and held is cast into a slab (thickness: from 400 to 600 mm, width: from 1,000 to 2,000 mm, length: from 2,000 to 6,000 mm). The slab obtained is subjected to a surface-cutting step where an impurity structure portion on the slab surface is cut off by from 3 to 10 mm using a surface cutting machine and then to a soaking treatment step where the slab is kept in a soaking pit at a temperature of from 480 to 540xc2x0 C. for from 6 to 12 hours so as to remove stress inside the slab and make the structure uniform. Thereafter, the slab is hot-rolled at a temperature of from 480 to 540xc2x0 C. into a thickness of from 5 to 40 mm and then cold-rolled at room temperature into a predetermined thickness. Furthermore, in order to have a uniform structure, the slab is annealed, thereby homogenizing the rolled structure. The thus-treated slab is then subjected to cold rolling into a predetermined thickness and corrected to obtain a plate having good flatness.
From the standpoint of energy savings and effective use of resources, it is demanded to use, as an aluminum support for lithographic printing plates, a general-purpose aluminum plate or an aluminum plate prepared by omitting the intermediate annealing treatment or soaking treatment from the production process of the aluminum plate.
However, when an aluminum support for lithographic printing plates is prepared using the above-described aluminum plate, streaking or treatment unevenness called plane quality unevenness is readily generated. This is considered to occur because the aluminum dissolving rate varies depending on the crystal orientation in the progress of a chemical dissolution reaction or the reaction of aluminum varies depending on the crystal orientation in the progress of electrochemical pitting reaction.
In other words, irregularities formed due to the difference in the dissolving rate in a chemical dissolution reaction or variations in the pitting reaction (e.g., number of pits, difference in the size) depending on the crystal orientation are viewed as streaking or plane quality unevenness.
The present invention relates to a method for producing an aluminum support for lithographic printing plates, which is free from generation of failures called streaking or plane quality unevenness, and also relates to a method for producing an aluminum support for lithographic printing plates, which is improved in the surface shape.
Furthermore, the present invention relates to a method for producing an aluminum support for lithographic printing plates, which has a surface shape free from generation of failures called streaking or plane quality unevenness.
Still further, the present invention relates to a method for surface roughening a lithographic printing plate aluminum support having an improved surface shape free from generation of failures called streaking or plane quality unevenness, and also relates to a method for producing an aluminum support for lithographic printing plates.
As a result of extensive investigations, the present inventors have found that when an aluminum plate subjected to an electrochemical surface roughening treatment, which is in a state such that smuts mainly comprising aluminum hydroxide are formed on the surface, is heat treated, streaking is difficult to occur in the afterward etching treatment.
Furthermore, the present inventors have found that when an aluminum plate is preliminarily surface-roughened in an aqueous hydrochloric acid solution before an electrochemical surface roughening treatment in an aqueous nitric acid solution, uniform honeycomb pits are formed. The present inventors have also found that when an electrochemical surface treatment in an aqueous hydrochloric acid solution is performed after an electrochemical surface roughening treatment in an aqueous nitric acid solution, an aluminum support for lithographic printing plates, having excellent printing capability can be obtained. The present inventors have also found that although an auxiliary anode is used in an electrochemical surface roughening treatment using AC so as to prevent the main electrode from dissolving, when an aqueous neutral salt solution is used as an electrolytic solution in the moiety using the auxiliary anode, dissolving of the aluminum plate takes place and the treatment steps can be reduced as compared with conventional systems involving chemical etching.
Still further, the present inventors have found that when an aluminum plate is subjected to a preliminary surface roughening treatment with an electricity quantity of from 1 to 300 C/dm2 using AC having a frequency of from 50 to 500 Hz and then subjected to an electrochemical surface treatment, streaking is difficult to occur in the afterward etching treatment.
Still further, the present inventors have found that when an aluminum plate is subjected to a preliminary surface roughening treatment with an electricity quantity of from 1 to 300 C/dm2 using AC having a frequency of from 50 to 500 Hz and then subjected to a desmutting treatment and further to an electrochemical surface roughening treatment, streaking is difficult to occur in the afterward etching treatment. The present inventors have also found that in a method where an aluminum support is preliminarily subjected to an electrochemical surface roughening treatment in an aqueous solution mainly comprising hydrochloric acid and then to a desmutting treatment in an acidic aqueous solution, when the desmutting treatment is performed while treating the aluminum plate by cathodic electrolysis using an auxiliary electrode cell of an electrochemical surface roughening apparatus, the desmutting treatment can be performed with good efficiency. The present invention has been accomplished based on these findings.
The practical embodiments of the method for producing an aluminum support for lithographic printing plates of the present invention are described in detail below.
Embodiment 1:
An aluminum plate is subjected to
(1) a surface roughening treatment,
(2) a heat treatment,
(3) a treatment of dissolving from 0.01 to 5 g/m2 of the aluminum plate, and then
(4) an anodization treatment,
whereby streaking is difficultly generated in the treatment of dissolving from 0.01 to 5 g/m2 of the aluminum plate performed before the anodization treatment.
The above-described surface roughening treatment is performed by combining one or more of a mechanical surface roughening treatment, a buffing treatment, a polishing treatment, a chemical etching treatment in an aqueous acid or alkali solution, an electropolishing treatment in an aqueous acid or alkali solution using the aluminum plate as an anode, an electrolytic treatment in an aqueous neutral salt solution using the aluminum plate as an anode or a cathode, and an electrochemical surface roughening treatment in an acidic aqueous solution using DC or AC.
Embodiment 2:
An aluminum plate is subjected to
(1) a chemical etching treatment,
(2) an electrochemical surface roughening treatment in an acidic aqueous solution,
(3) a heat treatment,
(4) a treatment of etching of from 0.01 to 5 g/m2 of the aluminum plate, and then
(5) an anodization treatment,
whereby streaking is difficultly generated in the treatment of dissolving from 0.01 to 5 g/m2 of the aluminum plate performed before the anodization treatment.
Embodiment 3:
An aluminum plate is subjected to
(1) a chemical etching treatment,
(2) a preliminary electrochemical surface roughening treatment in an aqueous hydrochloric acid solution with an electricity quantity of from 1 to 300 C/dm2,
(3) a treatment of etching from 0.01 to 3 g/m2 of the aluminum plate,
(4) an electrochemical surface roughening treatment in an acidic aqueous solution,
(5) a heat treatment,
(6) a treatment of etching from 0.01 to 5 g/m2 of the aluminum plate, and then
(7) an anodization treatment,
whereby streaking is difficultly generated in the treatment of dissolving from 0.01 to 5 g/m2 of the aluminum plate performed before the anodization treatment. Furthermore, by performing a preliminary electrochemical surface roughening treatment in an aqueous hydrochloric acid solution with an electricity quantity of from 1 to 300 C/dm2 before the electrochemical surface roughening treatment in an acidic aqueous solution, uniform pits can be formed in the acidic aqueous solution and also difficult viewing of streaks and improved printing capability can be attained.
Embodiment 4:
An aluminum plate is subjected to
(1) a chemical etching treatment,
(2) an electrochemical surface roughening treatment in an acidic aqueous solution,
(3) a treatment of etching from 0.01 to 5 g/m2 of the aluminum plate,
(4) an electrochemical surface roughening treatment in an aqueous hydrochloric acid solution with an electricity quantity of from 1 to 300 C/dm2,
(5) a heat treatment,
(6) a treatment of etching from 0.01 to 3 g/m2 of the aluminum plate, and then
(7) an anodization treatment,
whereby streaking is difficultly generated in the treatment of dissolving from 0.01 to 5 g/m2 of the aluminum plate performed before the anodization treatment. Furthermore, by performing an electrochemical surface roughening treatment in an aqueous hydrochloric acid solution with an electricity quantity of from 1 to 300 C/dm2 after the electrochemical surface roughening treatment in an acidic aqueous solution, difficult viewing of streaks and improved printing capability can be attained.
In Embodiments 1 to 4,
1) the heat treatment is preferably performed to raise the aluminum plate temperature to from 70 to 700xc2x0 C.,
2) the treatment of etching from 0.01 to 5 g/m2 of the aluminum plate is preferably a chemical etching treatment in an aqueous acid or alkali solution, an electropolishing treatment in an aqueous acid or alkali solution using the aluminum plate as an anode or an electrolytic treatment in an aqueous neutral salt solution using the aluminum plate as a cathode,
3) after the etching with an alkaline aqueous solution, after the electropolishing treatment in an aqueous alkali solution or after the electrolytic treatment in an aqueous neutral salt solution using the aluminum plate as a cathode, the aluminum plate is preferably desmutted in an acidic aqueous solution, and
4) before the first-step chemical etching treatment, a mechanical surface roughening treatment, a buffing treatment, or both a buffing treatment and a mechanical surface roughening treatment is(are) preferably performed; before the anodization treatment, a polishing treatment is preferably performed; and after the anodization treatment, a hydrophilization treatment is preferably performed.
The practical embodiments of the surface roughening method of electrochemically surface roughening an aluminum plate both before and after an electrolytic treatment in an aqueous neutral salt solution using the aluminum plate as a cathode, of the present invention are described in detail below.
Embodiment 5:
An aluminum plate is subjected in sequence to
(1) an electrochemical surface roughening treatment both before and after an electrolytic treatment in an aqueous neutral salt solution using the aluminum plate as a cathode,
(2) a treatment of dissolving from 0.01 to 5 g/m2 of the aluminum plate, and then
(3) an anodization treatment.
Embodiment 6:
An aluminum plate is subjected in sequence to
(1) a chemical etching treatment,
(2) a preliminary electrochemical surface roughening treatment in an aqueous hydrochloric acid solution with an electricity quantity of from 1 to 300 C/dm2,
(3) an electrolytic treatment in an aqueous neutral salt solution using the aluminum plate as a cathode,
(4) an electrochemical surface roughening treatment in an acidic aqueous solution,
(5) a treatment of etching from 0.01 to 5 g/m2 of the aluminum plate, and then
(6) an anodization treatment.
Embodiment 7:
An aluminum plate is subjected in sequence to
(1) a chemical etching treatment,
(2) an electrochemical surface roughening treatment in an acidic aqueous solution,
(3) a treatment of etching from 0.01 to 5 g/m2 of the aluminum plate,
(4) an electrochemical surface roughening treatment in an aqueous hydrochloric acid solution with an electricity quantity of from 1 to 300 C/dm2,
(5) an electrolytic treatment in an aqueous neutral salt solution using the aluminum plate as a cathode,
(6) a treatment of etching from 0.01 to 5 g/m2 of the aluminum plate, and then
(7) an anodization treatment.
Embodiment 8:
An aluminum plate is subjected in sequence to
(1) an electrochemical surface roughening treatment both before and after an electrolytic treatment in an aqueous neutral salt solution using the aluminum plate as a cathode,
(2) a heat treatment,
(3) a treatment of dissolving from 0.01 to 5 g/m2 of the aluminum plate, and then
(4) an anodization treatment.
In Embodiments 5 to 8,
1) the treatment of etching from 0.01 to 5 g/m2 of the aluminum plate is preferably a chemical etching treatment in an aqueous acid or alkali solution, an electropolishing treatment in an aqueous acid or alkali solution using the aluminum plate as an anode or an electrolytic treatment in an aqueous neutral salt solution using the aluminum plate as a cathode,
2) after the etching with an alkaline aqueous solution, after the electropolishing treatment in an aqueous alkali solution or after the electrolytic treatment in an aqueous neutral salt solution using the aluminum plate as a cathode, the aluminum plate is preferably desmutted in an acidic aqueous solution,
3) before the first-step chemical etching treatment, a mechanical surface roughening treatment or both a buffing treatment and a mechanical surface roughening treatment is(are) preferably performed; before the first-step chemical etching treatment, a buffing is preferably performed; before the anodization treatment, a polishing treatment is preferably performed; and after the anodization treatment, a hydrophilization treatment is preferably performed, and
4) the heat treatment is preferably performed to raise the aluminum plate temperature to from 70 to 700xc2x0 C.
The practical embodiments of the present invention are also described in detail below.
Embodiment 9:
A method for producing an aluminum plate for lithographic printing plates, comprising subjecting an aluminum plate in sequence to
(1) an etching treatment and/or a desmutting treatment in an acidic aqueous solution,
(2) a preliminary electrochemical surface roughening treatment in an aqueous hydrochloric acid solution with an electricity quantity of from 1 to 300 C/dm2 using AC of from 50 to 500 Hz,
(3) an electrochemical surface roughening treatment in an acidic aqueous solution,
(4) a treatment of etching from 0.01 to 5 g/m2 of the aluminum plate and/or a desmutting treatment in an acidic aqueous solution, and then
(5) an anodization treatment.
Embodiment 10:
A method for producing an aluminum plate for lithographic printing plates, comprising subjecting an aluminum plate in sequence to
(1) an etching treatment and/or a desmutting treatment in an acidic aqueous solution,
(2) a preliminary electrochemical surface roughening treatment in an aqueous hydrochloric acid solution with an electricity quantity of from 1 to 300 C/dm2 using AC of from 50 to 500 Hz,
(3) an electrochemical surface roughening treatment in an acidic aqueous solution,
(4) a heat treatment,
(5) a treatment of etching from 0.01 to 5 g/m2 of the aluminum plate and/or a desmutting treatment in an acidic aqueous solution, and then
(6) an anodization treatment.
Embodiment 11:
A method for producing an aluminum plate for lithographic printing plates, comprising subjecting an aluminum plate in sequence to
(1) an etching treatment and/or a desmutting treatment in an acidic aqueous solution,
(2) a preliminary electrochemical surface roughening treatment in an aqueous hydrochloric acid solution with an electricity quantity of from 1 to 300 C/dm2 using AC of from 50 to 500 Hz,
(3) a treatment of etching from 0.01 to 5 g/m2 of the aluminum plate and/or a desmutting treatment in an acidic aqueous solution,
(4) an electrochemical surface roughening treatment in an acidic aqueous solution,
(5) a treatment of etching from 0.01 to 5 g/m2 of the aluminum plate and/or a desmutting treatment in an acidic aqueous solution, and then
(6) an anodization treatment.
Embodiment 12:
A method for producing an aluminum plate for lithographic printing plates, comprising subjecting an aluminum plate in sequence to
(1) an etching treatment and/or a desmutting treatment in an acidic aqueous solution,
(2) a preliminary electrochemical surface roughening treatment in an aqueous hydrochloric acid solution with an electricity quantity of from 1 to 300 C/dm2 using AC of from 50 to 500 Hz,
(3) a treatment of etching from 0.01 to 5 g/m2 of the aluminum plate and/or a desmutting treatment in an acidic aqueous solution,
(4) an electrochemical surface roughening treatment in an acidic aqueous solution,
(5) a heat treatment,
(6) a treatment of etching from 0.01 to 5 g/m2 of the aluminum plate and/or a desmutting treatment in an acidic aqueous solution, and then
(7) an anodization treatment.
In Embodiments 9 to 12 of the present invention, a mechanical surface roughening treatment, a buffing treatment or both a buffing treatment and a mechanical surface roughening treatment is(are) performed before the first-step chemical etching treatment, so that a more suitable aluminum support for lithographic printing plates can be obtained.
The heat treatment is preferably performed to raise the aluminum plate temperature to from 70 to 700xc2x0 C.
In Embodiments 9 to 12 of the present invention, the treatment of etching from 0.01 to 5 g/m2 of the aluminum plate is a chemical etching treatment in an aqueous acid or alkali solution, an electropolishing treatment in an aqueous acid or alkali solution using the aluminum plate as an anode, an electrolytic treatment in an aqueous neutral salt solution using the aluminum plate as a cathode or an etching treatment comprising two or more of these treatments.
When a polishing treatment is performed before the anodization treatment, a more suitable aluminum support for lithographic printing plates can be obtained.
Furthermore, after the anodization treatment, a hydrophilization treatment is preferably performed.
Embodiment 13 of the present invention is a method for surface roughening an aluminum support for lithographic printing plates, comprising performing a preliminary electrochemical surface roughening treatment in an aqueous solution mainly comprising hydrochloric acid and then performing a desmutting treatment in an acidic aqueous solution, wherein the desmutting treatment is performed while treating the aluminum plate by cathodic electrolysis using an auxiliary electrode cell of an electrochemical surface roughening apparatus.
Embodiment 14 of the present invention is a method for surface roughening an aluminum support for lithographic printing plates, comprising subjecting an aluminum plate in sequence to
(1) an etching treatment and/or a desmutting treatment in an acidic aqueous solution,
(2) a preliminary electrochemical surface roughening in an aqueous hydrochloric acid solution with an electricity quantity of from 1 to 300 C/dm2 using AC having a frequency of from 50 to 500 Hz,
(3) a desmutting treatment while treating the aluminum plate by cathodic electrolysis in an acidic aqueous solution,
(4) an electrochemical surface roughening treatment in an acidic aqueous solution,
(5) a treatment of etching from 0.01 to 5 g/m2 of the aluminum plate and/or a desmutting treatment in an acidic aqueous solution, and then
(6) an anodization treatment.
In Embodiments 13 and 14 of the present invention, which is a method of performing a desmutting treatment in an acidic aqueous solution after the preliminary electrochemical surface roughening in an aqueous solution mainly comprising hydrochloric acid, the desmutting treatment is preferably performed while treating the aluminum plate by cathodic electrolysis using an auxiliary electrode cell of an electrochemical surface roughening apparatus.
Furthermore, in Embodiments 13 and 14 of the present invention, the solution for use in the desmutting treatment is preferably an aqueous solution mainly comprising hydrochloric acid, sulfuric acid or nitric acid, or a mixed solution thereof.
Still further, in Embodiments 13 and 14 of the present invention, the electrochemical surface roughening in an acidic aqueous solution is preferably performed with an electricity quantity of from 1 to 800 C/dm2.
Still further, in Embodiments 13 and 14 of the present invention, when a mechanical surface roughening treatment, a buffing treatment and a combination of buffing and mechanical treatments is performed before the first-step chemical etching treatment, a more suitable aluminum support for lithographic printing plates can be obtained.
Still further, in Embodiments 13 and 14 of the present invention, the heat treatment is preferably performed to raise the aluminum plate temperature to from 70 to 700xc2x0 C.
Embodiments 13 and 14 of the method of the present invention are described in detail below.
In the method of the present invention, the treatment of etching from 0.01 to 5 g/m2 of the aluminum plate is a chemical etching treatment in an aqueous acid or alkali solution, an electropolishing treatment in an aqueous acid or alkali solution using the aluminum plate as an anode, an electrolytic treatment in an aqueous neutral salt solution using the aluminum plate as a cathode or an etching treatment comprising two or more of these treatments.
When a polishing treatment is performed before the anodization treatment, a more suitable aluminum support for lithographic printing plates can be obtained.
Furthermore, in the present invention, a hydrophilization treatment is preferably performed after the anodization treatment.
The anodization treatment is preferably performed under the conditions such that the sulfuric acid concentration is from 100 to 200 g/l, the concentration of aluminum ion contained in the aqueous sulfuric acid solution is from 2 to 10 g/l and the liquid temperature is from 30 to 40xc2x0 C.
Alternatively, the anodization treatment is preferably performed under the conditions such that the sulfuric acid concentration is from 50 to 125 g/l, the concentration of aluminum ion contained in the aqueous sulfuric acid solution is from 2 to 10 g/l and the liquid temperature is from 40 to 70xc2x0 C.